The present invention relates to computer aided design systems and, more particularly, to a system which utilizes parameter checking for designing mechanical parts and which is particularly well suited for designing parts that are to be fabricated from sheet metal and the like.
Computer-Aided Design (CAD) systems are well known in certain fabrication arts. Typically, a CAD system comprises a graphic work station and computer software. Such a CAD system enables a designer to draw a part, view the part from various perspectives, and compute various data related to the part, such as the material needed to construct the part. In addition, a CAD system which is specifically designed for a known manufacturing process such as a semiconductor fabrication process may test the design by applying a predetermined set of design rules to find out whether the design satisfies the rules.
CAD systems in the mechanical fabrication arts are less sophisticated than those in such arts as the semiconductor fabrication arts in terms of their ability to test part designs. For example, currently available systems for designing mechanical parts to be fabricated of sheet metal require the designer to be knowledgeable in a set of design rules governing such matters as minimum permissible radii of curvature of bends and minimum spacings between a hole in a surface and edge of that surface. Testing a complicated mechanical design against such a set of rules can be a tedious, time-consuming process for a designer.
In addition to knowing these design rules, the designer must be thoroughly familiar with the tooling and fabrication methods of the shop in which the part is to be fabricated. A sheet metal part generally is fabricated by bending various portions of a flat sheet of metal. Any given shop has various machines and tools that are used to make such bends. The tools which are available, and the capabilities of those tools, vary from shop to shop. Requiring the designer to know the capabilities and limitations of a given shop places an undue burden on the designer and limits the efficiency of the design process.
Moreover, there usually are many different sequences in which a set of bends can be made. Different tools may be needed according to which sequence is selected. A sequence of fabrication steps specified by the designer may not be an optimum method for fabricating the part because the order in which various portions of an initially-flat sheet of material are bent can dramatically affect the yield and fabrication time. In fact, limitations of the available tooling sometimes make it impossible to make a part according to a sequence of bends specified by the designer. Requiring the designer to check a plurality of bending sequences against the available bending tools and processes to find an efficient order of bending to fabricate a complicated mechanical part is not practical.
CAD systems which provide a designer with design rules on an interactive basis have been proposed but have not adequately met the need for a system for designing mechanical parts, especially parts to be fabricated from sheet metal.
From the foregoing it will be apparent that there is a need for a CAD system that can automatically test a proposed design of a desired mechanical part against a set of parameters and that can determine an efficient process plan for making the part, including specifying a set of fabrication tools and a sequence of fabrication steps.